How To: Repair cracks in a concrete garage floor before applying paint or epoxy

Q. We have owned our home since it was constructed in 1984. The garage floor is now stained and cracked. We were going to paint it with a product advertised for use on garage floors. But we called the company and were told that the paint does not fill cracks. Do you have any advice about how to repair the cracks and remove or mask the stains? Is this something that homeowners can do on their own, or should we get a professional?

— Arlington County

A. It’s true that neither basic garage floor paint nor an epoxy coating for garage floors fills cracks, but that doesn’t mean you can’t patch the cracks and then paint. And yes, you can probably do it yourself.

With either paint or epoxy, you should first thoroughly clean the floor with a degreaser. Rust-Oleum, which makes the EpoxyShield line of garage floor coatings, markets its own cleaner (Rust-Oleum EpoxyShield Heavy-Duty Degreaser), but if you already have a general-purpose cleaner such as Simple Green, you can use that instead, says Rick Braunshausen, who answers technical questions for Rust-Oleum. You don't need to remove the discoloration, just the oily residue. There's a simple test for whether it's clean enough: If you splash on water, it should sink in, not bead up.

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Once the floor is clean and dry, patch the cracks and etch the surface before you paint. There are cement-based patch products, but Braunshausen recommends his company’s EpoxyShield Concrete Patch and Repair because you can apply the finish coat after eight hours, rather than waiting 28 days for a cement-based patch to cure. The company also makes an etching product, which completes the surface-preparation process.

Epoxy floor coatings, which are more durable than paint, usually come with vinyl chips that make the surface look like it’s scattered with confetti. “The chips make it look pretty and hide any whoops in the application,” Braunshausen says. They do not make the floor less slippery, which can be a big issue with epoxy, especially on a floor where rain or melting snow might drip off a vehicle. However, you can purchase an anti-slip additive separately and mix it into the epoxy before you apply it. And Rust-Oleum makes a clear coating with the anti-slip material that homeowners can use to retrofit floors that weren’t treated initially.

To make sure you buy all of the products you need in one trip, read instructions before you shop. For Rust-Oleum products, which are sold at Home Depot and many independent paint stores, find tech sheets and product labels at www.rustoleum.com. For a similar line of Quikrete products sold at Lowe's, go to www.quikretecoatings.com.

Have a problem in your home? Send questions to localliving@washpost.com. Put "How To" in the subject line, tell us where you live and try to inclue a photo of the project or item.

The Checklist: July is almost over. Read Jeanne Huber's roundup of home-improvement tasks you should tackle in August.

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